Manhole cover monitoring method and passive sensor used for monitoring

The invention relates to a manhole cover monitoring method and a passive sensor used for monitoring and belongs to the communication monitoring technology field. The method is mainly characterized inthat monitoring optical fibers are laid on each manhole pipeline; the monitoring optical fibers pass through the passive sensors fixedly arranged below manhole covers; open and close motions of the manhole cover can trigger the passive sensors to bend the monitoring optical fibers; the optical time domain reflectometer OTDR of one end of the monitoring optical fibers collects optical fiber loss data changes and the changes are transmitted to a system sever via Internet; and a system server end processing program processes optical fiber loss data, the position of the manhole on an optical pathis compared and open and close states of the manhole cover are determined. In the invention, dispersive pipeline manhole covers in a communication industry can be effectively managed and controlled; construction which can thre